Subject: Re: vixie-crontab vunerable?
To: Gordon W. Ross <>
From: David Brownlee <>
List: current-users
Date: 12/16/1996 21:06:00
On Mon, 16 Dec 1996, Gordon W. Ross wrote:

> > From: Bill Sommerfeld <>
> > 
> > Hmm.  Anyone for producing a "libcsafe" which doesn't include:
> > 
> > 	strcat
> > 	strcpy
> > 	sprintf
> > 	gets
> > 
> > and other "unsafe", but traditional, interfaces, and then linking all
> > setuid system programs against it instead of libc?
> You could also create a "libcsafe" that DOES include those functions,
> and ONLY those, but where those functions all just call abort.  You

	This feels wrong to me - you either want the program not to link
	at all, or to link and run. Having a program that links, then
	at some random time later aborts due to a little used code
	branch calling sprintf.... especially a daemon...

> might also make them invoke the magic link-time warning stuff.
	This seems better - possibly enabled via an option to gcc?
	The problem is that there are times when strcat, strcpy, & sprintf
	are perfectly safe - while gets is never right.

	snprintf usage is not guaranteed to be bugfree, just less likely
	to have a bug than sprintf.

	The best approach is probably for someome to go through the source
	tree checking all the suid programs for strcat, strcpy & sprintf
	usage. (I believe Theo has done a hell of a lot of this for
	OpenBSD). Non suid programs should ideally be checked as well, but
	it boils down to effective use of resources :)

	Maybe that suggested option to gcc should be enabled in
	the makefiles for suid programs?

		David/abs	david@{,,}

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